Mars angel and heart
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Credit: ESA/DLR/FU Berlin

Mars is revealing angel, devil and heart "tattoos" as ice at its south pole vaporizes

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Feb 17, 2021, 7:18 AM EST (Updated)

You know that heart you got tattooed on your hip when you were 18, and were relieved that your parents never found out? Even planets hide tattoos.

The Red Planet apparently has some ink. Now that its summer is warming up the Martian south pole and its ice is starting to sublimate (vaporize wtihout melting), ESA’s Mars Express spacecraft’s High Resolution Stereo Camera (HRSC) has revealed an angel, heart and devils “tattooed” on its nether regions. While these are permanent, like actual tattoos, they aren’t really some sort of alien ink. They are really formations that just happen to look like a mistake you made when you were a freshman in college—just much cooler.

"The strength of HRSC is to perform high resolution digital terrain models of the Martian surface in order to provide topographic context for the geoscientific evaluation of surface processes in space and time,” HRSC Principal Investigator Ralf Jaumann said in a press release.

Martian seasons last twice as long as Earth seasons (and a year is double what a year is on Earth) because of its longer orbit. The body art on Mars is usually covered up by ice around 250 miles across and nearly a mile thick. Not much of it is water ice, so future Mars-tronauts are going to have to look elsewhere for drinkable water that could also double as a source of hydrogen for rocket fuel, unless they want to dig. There might be subsurface water on the south pole, but most of its ice is actually frozen carbon dioxide, or dry ice. It doesn't melt with the heat but instead sublimates, or morphs straight from a solid to a gas. Co2 released from that dry ice makes the atmosphere thicker until winter freezes over again.

Credit: ESA/DLR/FU Berlin

 

As HSRC images Mars, it beams back hi-res, full-color 3D images that look almost unreal. Because it merges images at two different resolutions, its pointing accuracy is unprecedented.

So what really is that angel? Its hand is thought to be a sublimation pit that was left behind by dry ice after it sublimated. This is hardly the only sublimation pit on Mars, or in the solar system. Sometimes water sublimates on Earth and leaves behind similar pits. They can also be found on Pluto, especially in the Sputnik Plantitia region. These are probably the most similar to the Martian pits, except summer on Pluto is hardly warm enough to unfreeze anything. Sublimation of dry ice on Pluto probably happens because of sunlight randomly hitting the frozen carbon dioxide from over 3 billion miles away.

The angel got its halo in way that is anything but angelic. What gives it that deceptively ethereal look is actually an impact crater (which also formed the head). Some demonic forces from space, probably asteroids or meteorites, smashed into the planet and exposed subsurface layers that we otherwise wouldn’t be able to see. These are hardly the only impact craters on Mars. Perseverance will be touching down in Jezero Crater, which was formed by things slamming around in the early solar system and used to be a lake billions of years ago. The history of water means that microbial life might have been creeping around in there and could even be somewhere deep below the surface.

Speaking of angels, the devils past the angel’s left hand aren’t actually shaped like stereotypical devils. They are actually scratches left in the wake of dust devils that blew away surface dust and revealed the darker material underneath. Mars is a frozen desert, and since dust devils are not uncommon in the dry, thirsty areas of Earth, it should be no surprise that they are making extraterrestrial mischief.

At least Earthlings don’t have to go through asteroid bombardment for a sick tattoo.